Apparatus and method for the precision coating of strip



Oct. 8, 1968 R. D. FOLLRATH 3,405,006

APPARATUS AND METHOD FOR THE PRECISION COATING OF STRIP Filed Aug. 9, 1965 2 Sheets-Sheet l INVENTOR. 3 RICHARD. D. FOLLRATH Oct. 8, 1968 R. D. FOLLRATH 3,405,006

APPARATUS AND METHOD FOR THE PRECISION COATING OF STRIP Filed Aug. 9, 1965 2 Sheets-Sheet 2 INVENTOR. Fig. 4 RICHARD. D. FOLLRATH MZ/fiek United States Patent 3,405,006 APPARATUS AND METHOD FOR THE PRECISION COATING OF STRIP Richard'D. Follrath, Birmingham, Mich., assignor to Anaconda Wire and'Cable Company, a corporation of Delaware Filed Aug. 9, 1965, Ser. No. 478,355 11 Claims. (Cl. 117-213) My invention relates to an apparatus and method for applying precision coatings, such as insulating enamel coatings, to strip; and particularly to apparatus for applying such coatings to the edges as well as the faces of the strip.

In the manufacture of the insulated product that is widely known commercially as magnet strip conductor, copper or aluminum strip is coated with insulating enamel identical or similar to the enamels long used on magnet wire. The strip to which my invention is directed is very wide compared to its thickness, in a ratio of at least 20 to l, and usually in excess of 100 to 1. The enamel coating of the edges of such thin strip has proven to be very difficult and it is a feature of my apparatus and method that they are capable of applying a precise, uniform coating over both the faces and edges of magnet strip.

In this regard it should be noted that the requirements for the application of insulating enamels are much more exacting than the requirements for other types of coating, for the following reasons. In the first place the insulating enamel layer is very thin, ranging from about 0.00025 to 0.001 inch in thickness on a finished strip. This is necessitated by cost considerations but even more by space considerations since it is necesary to make as many ampere turns as possible in the space available for such electrical components as transformer coils, electromagnet coils, etc. In such components, as much of the available space as possible should be occupied by conducting metal, and as little as necessary by the insulation between turns. In the second place the dielectric integrity of the enamel layer must be high, and it must be substantially free from pin holes and weak spots. The enamel layer must be very uniform because any lumps will increase the space factor when the strip is wound into a coil and because the degree of curing of the enamel in a continuous process is' a function of the enamel thickness, and any spots that are too thick or too thin will be respectively undercured or overcured. Whereas apparatus has been known to apply paint coatings to strip and to flat members, such as slats for venetian blinds, and have the coatings flow over the edges, as well as the faces of such members, the known apparatus is not capable of applying accurately metered or precision coatings both to the faces and to the edges of strip.

In my copending application Ser. No. 373,159, now Patent No. 3,336,778, I have disclosed apparatus for forming rounded edges on magnet strip. I have now discovered that the faces or fiat surfaces of the strip can be precisely enamelled along with the rounded edges by means of apparatus comprising resilient-surfaced applicator rolls rotated against the motion of the strip. My new apparatus may be used with strip having edges rounded by rolling, grinding, etching or other means and is not limited to the strip of the above-mentioned application.

My new apparatus for applying a coating to the faces and edges of advancing strip comprises means advancing the strip, preferably upwardly, and a pair of applicator rolls mounted on parallel axes on either side of the strip. The rolls are longer than the strip is wide, and extend beyond the edges of the strip. The rolls have resilient or rubber-like surfaces and there are means urging them together and bringing their surfaces into contact beyond the edges of thestrip. My apparatus also comprises means rotating the rolls in directions opposed to the advance of the strip and means continuously applying a coating to the rolls,-this coating being continuously transferred from the rolls tothe faces and entire edges of the strip.

In a preferred embodiment my apparatus also cornprises a pair of doctor rolls mounted on axes parallel to the axes of the applicator rolls, the doctor rolls also extending beyond the edges of the strip. In this embodiment there are means applying coatings to the doctor rolls which transfer them to the applicator rolls. The doctor rolls are preferably driven in the opposite rotational direction to the contacting applicator rolls, but at a reduced surface speed so that the surfaces slide upon each other. I have also provided means urging the doctor rolls against the applicator rolls with a force of at least 50 pounds per linear inch.

In a preferred embodiment of my invention the rolls are mounted on a pair of frames, ther are hinge means supporting the frames swingable away from the strip so that the rolls can be separated for the passage of splices, and for threading the strip into the apparatus. Air cylinders or other means urging the'frames to swing around the hinge means serve to press the applicator rolls together and against the strip. a

A method utilizing the apparatus of my invention for applying a coating such as an enamel solution coating between 1 and 5 mils thick to the faces and edges of a strip such as magnet strip having rounded edges comprises the following steps: the edges of the strip are rounded. The strip is continuously advanced upwardly and an excess coating is applied to the edges only, by means such as felt applicators. The strip is then passed between a pair of resilient applicator rolls that rotate in opposition to the advancing strip while the rolls are urged so as to be compressed together beyond the edges of the strip and into contact with the entire perimeter of the faces and edges of the strip. A coating is applied'to the applicator rolls, by means such, preferably, as doctor rolls that rotate at a lower surface speed than the applicator rolls. The applicator rolls transfer the coating, whichpreferably has a viscosity of -2500 centipoises, over the faces and edges of the strip.

A more thorough understanding of my invention can be gained from the appended drawing.

In the drawing:

FIGURE 1 shows a side view of the apparatus of my invention. I

FIGURE 2 shows a front view of half of the apparatus of FIGURE 1.

FIGURE 3 shows a section through the line 33 of FIGURE 1.

FIGURE 4 shows a feature used in one method of practicing my invention.

In the apparatus of FIGURES 1 and 2 a platform 11 supports two frames 12, 13 each comprising two plates between which there are mounted applicator and doctor rolls. The frame 13 comprises plates 16, 17 connected by a member 18 which also serves as a shelf for a catch basin 19. The frame 13 is supported on two swivels 21, 22, the latter of which also serves as a journal for a drive shaft 23 on which are mounted a gear 24 and sprockets 26, 27. Between the plates 16, 17 there is mounted an applicator roll 28, on a shaft 29 rotatably supported in bearings 31, 32. A sprocket 30 is keyed to the shaft 29 for driving the shaft from the sprocket 27 by means of a chain 33. The roll 28 has a resilient surface layer 34 which I prefer to be solid natural rubber having a Shore A Durometer hardness of 55. The thickness of the surface 34 is relatively great. For example a roll having a total diameter of about 6 inches will have a resilient surface about 1 inch thick. It will be understood that other resilient or rubberlike materials such as neoprene can be used to surface the roller 28 but they should have a Shore A Durometer between 30 and 90 and, of course, must be thoroughly compatible with the enamelling solution.

A chrome-plated doctor roll 36 is mounted parallel to the roll 28 between the plates 16 and 17. The roll 36 has a shaft 37 supported in bearings 38, 39 which are mounted in slidable bearing blocks of which only a block 41 in the plate 16 can be seen in FIGURE 1. The block 41 is fastened to a rotatable threaded shaft 42. A bracket 43 is welded to the plate 16 and a nut 44 is welded to the bracket with the shaft 42 fitting through the nut 44. By means of a hand crank 46 and a similar hand crank at the plate 17, the shaft 42 can be turned in the nut 44 and a similar shaft turned at the other end of the roll 36 to urge the roll 36 against the roll 28. A sprocket 47 is fastened to the shaft 37 by means of which the roll 36 can be driven by the chain 33. The plate 16 mounts an idler sprocket 48 to take up slack in the chain 33 and the chain is passed around the sprockets 27, 48, 47 and 30 so as to rotate the roll 28 counterclockwise (as seen in FIGURE 1) and rotate the roll 36 clockwise. The sprocket 47 is much larger than the sprocket 30 so that, although the two rolls have approximately the same diameter the doctor roll 36 rotates only about 20 rpm. compared to 60 r.p.m. for the applicator roll 28.

A feed lpan 49 with an overflow pipe that drains into the catch basin 19 is fitted against the upwardly turning surface of the doctor roll 36. Enamel coating material is fed into the pan 49 through a tube 51 from a supply not shown. A bottom edge 52 and side edges 53, 54 of the pan 49 have close clearances from the surface of the roll 36, to prevent coating material from oozing through these clearances and dripping into the basin 19. The rolls 28, 36 are driven by a variable speed motor connected by means of a chain 55 to the sprocket 26. The assembly associated with the frame 13 has been described. The assembly of the matching frame 12 is identical except that a shaft 56 corresponding to the shaft 23 does not bear any sprocket corresponding to the sprocket 26 but is driven instead by the gear 24 meshing with a similar gear 57 on the shaft 23. On the frame 12 there is a rubber-surfaced applicator roll 58 corresponding to the roll 28 and a doctor roll 59 corresponding to the roll 36. The roll 58 is driven at the same speed but opposite rotational direction as the roll 28 and the roll 59 is driven in the opposite direction but same speed as the roll 36; rolls 58 and 59 being driven by a chain 61 turning on a sprocket keyed to the shaft 56 and similar to the sprocket 27.

The frames 12 and 13 are urged together by air cylinders 62, 63, the frames pivoting around the hinge means 21, 22 for frame 13 and corresponding hinge means coaxial with the shaft 56 for the frame 12. When the frames 12, 13 are urged together the rolls 28, 58 meet at a line 64 in the plane of a strip 66 which is advanced upwardly from a supply of strip not shown through a slot 67 in the platform 11, between the rolls 28, 58 and into an oven, not shown.

It is a feature of my invention that the force urging the rolls 58, 28 together must be great enough, and the resiliency of the roll surfaces must be such that the surfaces of the rolls will meet in spite of the presence of the strip 66 between them. Referring to FIGURE 3 the strip 66 is seen to have two faces 68, 69 and rounded edges 71, 72. These are entirely surrounded by the rubber surfaces of the rolls due to their resiliency and to the pressure between them created by the air cylinders 62, 63. Thus in the upward passage of the strip the rolls make line contact, and, in fact, due to the pressure of the rolls, surface contact with every point on the surface of the strip including the surface of the rounded edges. Coating is transferred to the faces and to the entire edges of the strip by the rolls 28, 58. In this regard it should be noted that the rolls are not merely rolling over the surfaces of the strip 4 I as it passes between them but are turning at relatively hi'g speed in a manner to oppose the upward advance of the strip. The latter is being pulled up through the rolls by a take-up mechanism, which is not shown in the drawing, of which a number of suitable types are known. By mounting the rolls on frame assemblies hinged at the bottom as described, I am able to separate the rolls for the purpose of threading the strip into my apparatus, and permitting the passage of any splices or other lumps, in the strip, without damaging the rolls.

In FIGURE 4 edge applicators 73, 74 have been mounted beneath the rolls 28, 58 to apply additional coating to the edges before they reach the rolls. These applicators are comprised of cylindrical containers 76, 77 from which felt wipes or pads 78, 79 project against the edges 71, 72. Excess coating applied to the edges is removed by the rolls 28, 58 and returned to the doctor rolls 36, 59. Fresh coating material is introduced dropwise into the containers 76, 77 from tubes 81, 82 supplied from conventional sources not shown.

OPERATION The operation of my apparatus may best be illustrated by considering a typical magnet strip conductor with the understanding that other sizes and conditions of operation will fall within the scope of my invention.

A coil of four-inch-wide metal strip with accurately rounded edges is mounted to have the strip feed up through the slot 67 between the applicator rolls 58, 28 and through a drying and baking oven of conventional type located above the applicator rolls. The strip is pulled through the apparatus at a rate of 60 feet per minute by means of a take-up mechanism of known type. Enamel coating material is continuously fed into the pan 49 through the tube 51 and through a similar tube 84 into a matching pan 83 associated with the doctor roll 59. The rolls 59, 36 are rotated upwardly through the pans 83, 49 and are coated with the coating which is adjusted to have a viscosity of 1002500 centipoises and preferably 300500 centipoises. The rolls 59, 36 have been pressed against the respective rolls 58, 28 to a pressure of pounds per linear inch. Since the rolls are all 16 inches long this amounts to a. 'force of 1200 pounds urging each pair of rolls together. This force can be varied as a means of controlling the thickness of coating applied to the strip, but in no case should it be less than about 50 pounds per linear inch length of the rolls. The doctor rolls carry the coating up to and deposit it upon the applicator rolls 58, 28. At the same time they serve to regulate the thickness of coating remaining on the applicator rolls. The coating thickness is controlled not only by the pressure between the rolls, greater pressure having the effect of decreasing the coating thickness, but by the speed of rotation of the doctor rolls. In the instant case, the doctor rolls, which have a diameter of about six inches which is the same diameter as the applicator rolls, are roated at about 20 r.p.m. As the strip passes upward between the applicator rolls a thin coating of enamel is deposited over its entire surface including the entire surface of the edges. There is no noticeable bank or pool of coating material trapped above the rolls and the deposited coating is thin being only about 0.002 inch thick. By means of the air rams 62, 63 the rolls 58 and 28 are compressed together beyond the edges of the strip, thus assuring the coating of the entire surface of the edges. The strip passes upward through a drying and baking oven, not shown, of which several satisfactory types are known. In the oven the coating is transformed to a dry enamel layer 0.1 to 0.5 mil thick. Since it is usually desirable to build up a wall of enamel that is from A to 1 mil thick, when it is dry, the operation so far described will be repeated from one to four more times in the process of forming a magnet strip.

The operation herein described is satisfactory for the manufacture of magnet strip of a wide range of thicknesses from several mils to 50 mils or more, and to greater widths by the substitution of longer rolls. If the rounding of the edges is somewhat irregular it is helpful to apply an extra coating of enamel to the edges only, by means of the pads 78, 79. The coating is applied below the applicator rolls and the latter wipe oif-any'excess-enamel. ,The apparatus and method hereinabove described are understood to be exemplary rather than definitive. Other embodiments and modifications coming within the full scope of my invention are defined in the following claims.

I claim: 1. Apparatus continuously applying a coating to the faces and edges of a flat strip comprising:

(A) means advancing said strip,

(B) a pair of applicator rolls mounted on parallel axes I on either side of said strip,

(a) said rolls extending beyond the edges of said strip, and

(b) said rolls having resilient surfaces,

(C) means urging together said rolls so as to bring said surfaces into contact beyond the edges of said strip,

(D) means rotating said rolls in directions opposed to the direction of advance of said strip, and

(E) means continuously applying a coating to said rolls,

said coating being continuously and uniformly transferred 'from said rolls to the faces and entire edges of said strip.

2. Apparatus continuously applying a coating to the faces and edges of a fiat strip comprising:

(A) means advancing said strip,

(B) 'a pair of applicator trolls mounted on parallel axes on either side of said strip,

(a) said rolls extending beyond the edges of said strip, and

(b) said rolls having solid resilient surfaces,

(C) means urging together said rolls so as to bring said surfaces into pressure contact beyond the edges of said strip,

(D) means rotating said rolls in directions opposed to .the direction of advance of said strip,

(E) a pair of doctor rolls mounted on axes parallel to the axes of said applicator rolls,

(a) said doctor rolls extending beyond the edges of said strip, and

(F) means applying a coating to said doctor rolls,

(a) said doctor rolls continuously transferring said coating to said applicator rolls and (b) said applicator rolls continuously and uniformly transferring said coating to the faces and entire edges of said strip.

3. Apparatus continuously applying a coating to the faces and edges of a fiat strip comprising:

(A) means advancing said strip,

(B) a pair of applicator rolls mounted on parallel axes on either side of said strip,

(a) said rolls extending beyond the edges of said strip, and

(b) said rolls having solid resilient surfaces,

(C) means urging together said rolls bringing said surfaces against the faces and edges of said strip and into pressure contact beyond the edges of said strip,

(D) means rotating said rolls in directions opposed to the direction of advance of said strip,

(E) a pair of doctor rolls mounted on axes below and parallel to the axes of said applicator rolls,

(a) said doctor rolls extending beyond the edges of said strip, and

(b) said doctor rolls being each in surface contact with a different one of said applicator rolls,

(F) means driving said doctor rolls,

(a) each of said doctor rolls being driven in the opposite rotational direction to its contacting applicator roll but at a reduced surface speed so that the surfaces slide upon each other, and

(G) means applying a coating to said doctor rolls,

(a) said doctor rolls continuously and uniformly transferring said coating to said applicator (T0118 and 1 (b) said applicator rolls continuously transferring said coating to the faces and entire edges of said strip.

4..Apparatus continuously applying a coating to the faces and edges of a flat strip comprising: t

(A) means upwardly advancing said strip,

.. (B) a pair of applicator rolls mounted on parallel axes on either side of said strip,

(a) said rolls extending beyond the edges of said strip, and

(b) said rolls having solid rubberlike surfaces,

(C) means urging together said rolls bringing said surfaces against the faces and edges of said strip and into pressure contact beyond the edges of said strip,

(D) means rotating said rolls downwardly at the faces of said strip,

(E) a pair of doctor rolls mounted on axes below and parallel to the axes of said applicator rolls and in surface contact with said applicator rolls,

(F) means driving said doctor rolls in opposite rotational directions to their contacting applicator rolls, the surface speed of said doctor rolls being lower than the surface speed of said applicator rolls,

(G) means adjustably urging said doctor rolls against said applicator rolls thereby controlling a thickness of coating on said applicator rolls, and

(H) means applying a coating to said doctor rolls,

(a) said doctor rolls continuously and uniformly transferring said coating to said applicator rolls, and

(b) said applicator rolls continuously transferring said coating to the faces and entire edges of said strip.

5. The apparatus of claim 4 wherein said adjustable urging means applya force of at least 50 pounds per linear inch between said doctor rolls and said applicator rolls.

6. Apparatus continuously and uniformly applying a coating to the faces and edges of a'flat strip comprising:

(A) means upwardly advancing said strip,

(B) a pair of frames mounted on either side of said strip,

- (C) hinge means supporting the bottom portions of said frames whereby said frames are swingable away from said strip,

(D) applicator rolls mounted on said frames,

(a) said rolls opposing each,other on opposite sides of said Strip,

(b) said rolls having resilient surfaces,

(E) means rotating said rolls downwardly at the faces of said strip,

(F) means continuously applying a coating to said rolls, and

(G) means urging said frames to swing around said hinge means so as to bring together said rolls against said strip.

7. Apparatus continuously applying a coating to the faces and edges of a flat strip comprising:

(A) means upwardly advancing said strip,

(B) a pair of frames mounted on either side of said strip,

(C) hinge means supporting the bottom portions of said frames whereby said frames are swingable away from said strip,

(D) applicator rolls mounted on said frames,

(a) said rolls having resilient surfaces (b) extending beyond the edges of said strip,

(c) said rolls opposing each other on opposite sides of said strip,

(E) means driving said rolls to rotate downwardly at the faces of said strip,

(F) "doctor rolls mounted on said frames (a) beneath said applicator rolls and (b) parallel thereto, (c) said doctor rolls being in surface contact with said applicator rolls,

(G) means driving said doctor rolls in opposite rotational directions to their contacting applicator rolls, the surface speed of said doctor rolls being lower than the surface speed of said applicator rolls,

(H) means mounted on said frames urging said doctor rolls in compression against said applicator rolls,

(1) means applying a coating to said doctor rolls,

(a) said doctor rolls continuously transferring said coating to said applicator rolls, and (b) said applicator rolls continuously and uniformly transferring said coating to the faces and entire edges of said strip, and

(1) means urging said frames to swing around said hinge means so as to bring together said applicator rolls against said strip and into pressure contact beyond the edges of said strip. 1

8. The method of applying a uniform coating to the faces and edges of a flat strip having rounded edges comprising the steps of:

(A) continuously upwardly advancing said strip,

(B) applying excess coating to the edges only of said strip,

(C) passing said strip between a pair of rolls having solid resilient cylindrical outer layers,

(a) said rolls rotating in opposition to the advancing of said strip,

(D) urging said rolls together so as to compress said layers together beyond the edges of said strip, and

against the entire edges of said strip, and

(E) applying a coating to said rolls, said rolls transferring said coating over the faces and edges of said strip and wiping the excess coating from the edges of said strip.

9. The method of applying a uniform coating between 1 and 5 mils thick to the faces and edges of magnet strip having rounded edges comprising the steps of:

(A) continuously upwardly advancing said strip,

(B) applying excess coating to the edges only of said strip,

(C) passing said strip between a pair of applicator rolls having solid resilient outer layers,

(a) said rolls rotating in opposition to the advancing of said strip,

(D) urging said rolls together so as to compress said layers together beyond the edges of said strip, and

(E) applying a coating to said rolls by means of doctor rolls rotating at a surface speed lower than the surface speed of said applicator rolls, said applicator rolls transferring said coating over the faces and edges of said strip and wiping the excess coating from the edges of said strip,

(a) said coating having a viscosity of -2500 centipoises.

10. The method of manufacturing an insulated magnet strip comprising the steps of:

(A) rounding the edges of said strip,

(B) passing said strip between a pair of rolls having solid resilient cylindrical outer layers,

(a) said rolls rotating in opposition to the advancing of said strip,

,(C) urging said rolls together and compressing said layers into contact with the entire perimeter of the faces and edges of said strip, and

(D) applying a coating to said rolls, said rolls transferring said coating over the faces and entire edges of said strip.

11. The method of manufacturing magnet strip concluctor having an insulation comprising a plurality of dry enamel layers each 0.1 to 0.5 mil thick comprising the steps of:

(A) rounding the edges of said strip,

(B) continuously upwardly advancing said strip having rounded edges,

(C) passing said strip between a pair of applicator rolls having solid resilient outer layers,

(a) said rolls rotating in opposition to the advancing of said strip,

(D) urging said rolls together and compressing said layers into contact with the entire perimeter of the faces and edges of said strip, and

(E) applying a coating to said rolls by means of doctor rolls rotating at a surface speed lower than the surface speed of said applicator rolls, said applicator rolls transferring said coating over the faces and entire edges of said strip,

(a) said coating having a viscosity of 100 to 2500 centipoises,

(F) drying said coating, and

(G) repeating said steps with each of said plurality of layers.

References Cited UNITED STATES PATENTS WILLIAM L. JARVIS, Primary Examiner. 

8. THE METHOD OF APPLYING A UNIFORM COATING TO THE FACES AND EDGES OF A FLAT STRIP HAVING ROUNDED EDGES COMPRISING THE STEPS OF: (A) CONTINUOUSLY UPWARDLY ADVANCING SAID STRIP, (B) APPLYING EXCESS COATING TO THE EDGES ONLY OF SAID STRIP, (C) PASSING SAID STRIP BETWEEN A PAIR OF ROLLS HAVING SOLID RESILIENT CYLINDRICAL OUTER LAYERS, (A) SAID ROLLS ROTATING IN OPPOSITION TO THE ADVANCING OF SAID STRIP, (D) URGING SAID ROLLS TOGETHER SO AS TO COMPRESS SAID LAYERS TOGETHER BEYOND THE EDGES OF SAID STRIP, AND AGAINST THE ENTIRE EDGES OF SAID STRIP, AND (E) APPLYING A COATING TO SAID ROLLS, SAID ROLLS TRANSFERRING SAID COATING OVER THE FACES AND EDGES OF SAID STRIP AND WIPING THE EXCESS COATING FROM THE EDGES OF SAID STRIP. 